Patent Document 1 discloses a vehicle seat reclining device that includes a first and second rotating members and a locking member. The first rotating member is arranged coaxially with the second rotating member. The locking member is capable of limiting relative rotation between the first and second rotating members. The seat reclining device disclosed in Patent Document 1 further includes a first memory member and a second memory member. The first memory member frictionally engages with the outer surface of the first rotating member. The second memory member is capable of restricting the first memory member from rotating relative to the second rotating member by engaging with the first memory member at a predetermined relative rotation position. During so called the walk-in access enabling action, in which the seat back is folded forward to facilitate entry into and exit from the rear seat, the locking member is either locked or unlocked in conjunction with engagement/disengagement of the second memory member with the first memory member. This allows the seat back, which has been folded forward, to be returned to the inclined position at which the seat back was located before the forward folding operation.
That is, many of conventional seat reclining devices have an operation handle on the side of the seat. The operation handle is manipulated to cause the locking member to cancel the constraint between the first and second rotating members, so that the tilt angle of the seat back can be adjusted. At the normal reclining operation, the seat reclining device disclosed in Patent Document 1 causes the second memory member to engage with the first memory member to restrict the first memory member from rotating relative to the second rotating member. The first rotating member is allowed to rotate relative to the second rotating member by acting against the frictional engagement force between the first rotating member and the first memory member.
In contrast, at the walk-in access enabling action, the locking member is unlocked in conjunction with separation of the second memory member from the first memory member. That is, when the second memory member is separated from the first memory member, the first memory member and the first rotating member rotate integrally due to the frictional engagement force between the first memory member and the first rotating member. Then, when the forward folded seat back is raised, the second memory member is engaged with the first memory member at a predetermined relative rotation position, so that the seat back is returned to the inclined position at which the seat back was located before the forward folding operation.
The seat reclining device of Patent Document 1 employs a shaft-shaped memory pin as the second memory member. Further, the seat reclining device includes a plate-shaped member, which has an elongated guide hole for receiving the memory pin. One end of the memory pin is coupled to a link member. When receiving operational force via the link member, the memory pin is engaged with or disengaged from the first memory member.